Technical datasheet MFSPM230212 - D-Marc Datash… · Technical datasheet MFSPM230212 Executive...
Transcript of Technical datasheet MFSPM230212 - D-Marc Datash… · Technical datasheet MFSPM230212 Executive...
Technical datasheet MFSPM230212
Executive summary
Mechanically affixed single ply membranes are susceptible to Wind-induced
suction which can repeatedly lift the membrane between the attachment
points and cause membrane elongation and billowing. The forces generated
when the membrane billows are high enough to move a D-marc base.
Research paper
Construction Technology Update No.55
“Dynamic Wind Testing of Commercial Roofing Systems” A. Baskaran. Institute for research
in construction, National Research Council of Canada.
Key Findings
Wind passing over and around a building with a low-slope roof (Figure 1a) exerts positive
pressure on the windward wall, negative pressure (suction) on the leeward wall and the
walls parallel to the flow direction, and suction over most of the roof area. The suction
generated at any particular roof location depends on the wind speed, wind direction,
turbulence intensity or gusts, building topography, building geometry and architectural
features, and varies with time. Commercial roofs, with their almost-flat profiles and low
parapets, are likely to experience high local suction pressures along the roof perimeter.
Figure 1b. Wind Effects on mechanically affixed single ply
Waterproof membranes are attached to the structural roof deck using fasteners (Figure 1b).
The attachment locations are then overlapped with another membrane sheet and the upper
and lower sheets seamed together. Wind-induced suction repeatedly lifts the membrane
between the attachments and causes membrane elongation and billowing. The magnitude
of the wind-induced suction and the membrane’s elastic properties determine
the extent of billowing.
It is this billowing effect that can cause products placed upon the roof surface to suffer from
uplift. The billowing force can be of a magnitude far greater than that exerted by the mass of
the D-marc base. Hence instability, leading to potential product failure can occur.
Conclusion
Roof covering manufacturer advice should be sought when considering the
installation of D-marc on mechanically affixed single ply roofing systems in
areas susceptible to high wind loads.